1. Field of the Invention
The present invention relates to a printed circuit board and a method for manufacturing the same.
2. Description of the Related Art
In recent times, miniaturization and technology integration of electronic devices and products have been steadily developed due to advance of the electronic devices and products. In addition, various changes in a manufacturing process of printed circuit boards used in the electronic devices and products are also needed in response to miniaturization and technology integration.
A technical direction for a method for manufacturing a printed circuit board has been developed from a single-sided printed circuit board to a double-sided printed circuit board at an early stage and to a multilayer printed circuit board again. Especially, recently, in manufacturing a multilayer printed circuit board, a manufacturing method, which is called a build-up method, is being developed.
Meanwhile, in a manufacturing process of printed circuit boards, a process of forming various via holes such as an inner via hole (IVH), a blind via hole (BVH), and a plated through hole (PTH) is needed to electrically connect between a circuit pattern and an electronic element of each layer. In the prior art, after forming a via hole in a base substrate, when plating is performed on upper and lower surfaces of the base substrate including an inner surface of the via hole and plating for interlayer electrical connection is completed, circuit patterns including pads are formed on the upper and lower surfaces of the base substrate so that solder balls or bumps are mounted on the pads.
However, when manufacturing a printed circuit board in accordance with the prior art, it is difficult to stably mount the solder ball due to limitation on bonding strength between the solder ball and the pad. That is, the bonding strength between the solder ball and the pad is affected by a step between the pad and a resist formed on the pad. When the step between the pad and the resist is small, the bonding strength between the solder ball and the pad is reduced. On the contrary, when the step between the pad and the resist is large, since a thickness of the printed circuit board is increased, it is difficult to respond to a demand for high density and thinning of the printed circuit board.
Due to this, there is a problem of degradation of reliability of the entire product having the printed circuit board.